1. Field of the Invention
This invention relates to a production process for a multicolor heat transfer recording paper, more particularly to a process for producing a multicolor heat transfer recording paper by using hot-melt inks having different melting points.
2. Description of the Prior Art
In the art of thermo-sensitive recording using thermal recording devices such as thermal printer or thermal facsimile, the so-called heat transfer recording system which has many advantageous features such as good keeping quality, indelibility and solvent resistance of the records has been developed and reached the stage of practical use. According to this system, a specific heat transfer recording paper having a hot-melt ink layer on a support is used, and in recording, a plain paper is placed on the ink layer side of said recording paper so that the ink is transferred from the heat transfer recording paper to the plain paper with the aid of heat from the thermal head of a thermal recording device such as thermal facsimile.
Monocolor (such as black-color) heat transfer recording by this system has already been applied to commercial use, and now the studies are directed to the realization of multicolor heat transfer recording by this system. Some remakable achievements have been disclosed in the official patent gazettes and other publications. For instance, Japanese Patent Laid-Open No. 182488/82 discloses a multicolor heat transfer recording paper having the ink layers of three basic colors of red, blue and yellow with a black ink layer provided for every trio of said basic color ink layers, said ink layers being formed on the principal surface of a base paper. In Japanese Patent Laid-Open No. 182489/82 is proposed a heat transfer recording paper having the groups of ink layers of different colors, the respective layers in each groups being varied in their area of occupancy in proportion to the frequency of use. Further, Japanese Patent Laid-Open No. 182490/82 reveals a heat transfer recording paper in which the ink layers of different colors are arranged in the sub-scanning direction.
According to these prior art devices, however, the transfer recording necessitates proper positioning of the recording paper in correspondence to the color to be transferred. This not only complicates the mechanisms of the recording system and the carrying and driving system of the apparatus but also makes it difficult to adapt the device to the speed-up of recording operation.
As an improvement over said prior art devices, Japanese Patent Laid-Open No. 187296/82 proposes a heat transfer recording paper in which a transfer layer containing the ink capsules of at least three primary colors (red, blue and yellow) is formed on the principal surface of base paper, said capsules of the respective colors being varied in melting point from each other. The patent states that, with this device, it is possible to obtain the transfer images of desired colors by merely controlling the temperature of the thermal head, and the apparatus can be simplified.
This device, however, has the drawbacks that the microcapsules containing hot-melt inks are hardly broken at their-walls even under application of a high voltage, and the transferred image are also unsatisfactory in their color development.